The present invention relates to an actuation device for opening and closing blades for defining a light path, i.e. diaphragm or stop, of a camera.
Conventionally, the light path for a camera is defined by a plurality of blades for constituting a diaphragm, which are moved by an actuation device attached to the blades. A conventional actuation device including the actuation device and the blades is shown in Japanese Utility Model Publication (KOKAI) No. 64-55931 published on Apr. 6, 1989.
As shown in FIGS. 1 and 2, the conventional actuation device A is formed of a permanent magnet 1 with an axle 2 attached to the magnet 1, and a frame 4 formed of frame portions 4a, 4b. Each of the frame portions 4a, 4b includes a central hole portion h, upper and lower hole portions d1, d2 and a groove e. The magnet 1 is disposed in the central hole portion h, and the axle 2 is disposed in the upper and lower hole portions d1, d2. Washers 3a, 3b are attached to the frame 4 for holding the axle 2. When assembled, the magnet 1 is rotationally retained inside the frame 4, and the frame 4 is situated inside a hollow magnet circuit member or yoke 7.
Actuation and brake coils (not shown) are situated in the grooves e. For example, the actuation coil for providing rotational force to the permanent magnet 1 is wound around the groove e in the frame portion 4a, while the brake coil for providing brake force to prevent rotation of the permanent magnet 1 actuated by the actuation coil is wound around the groove e in the frame portion 4b.
The frame portion 4a is provided with pins 5a, 5b for connecting ends of the actuation coil, while the frame portion 4b is provided with pins 6a, 6b for connecting ends of the brake coil. At a portion c of the frame 4b, a magnetic sensor 8 for sensing an angular position of the magnet 1 is situated. The sensor 8 is fixed on a printed board 9 placed on the frame 4 and connected to the pins 5a, 5b, 6a, 6b.
When the device A is assembled, the frame portions 4a, 4b are connected together after the magnet 1 is situated in the hole h. Then, the pins 5a, 5b, 6a, 6b are placed onto the frame 4, and the actuation and brake coils are wound in the grooves e. Thereafter, the printed board 9 is placed over the frame 4. Finally, the assembled frame 4 is inserted into the hollow magnet circuit member 7.
In the device A, since the pins 5a, 5b, 6a, 6b are situated on the respective frame portion 4a, 4b, the pins can not be freely arranged on the frame. The ends of the coil at the frame portion 4 a must be attached to the pins 5a, 5b, while the ends of the coil at the frame portion 4b must be attached to the pins 6a, 6b.
Further, since the pins 6a, 6b are attached to the periphery of the frame 4b, the length L2 is inevitably smaller than the length L1 of an attaching portion for the sensor 8. Therefore, in the device A, the printed board 9 must be attached to the frame 4 before the frame 4 is inserted into the magnet circuit member 7. Also, the printed board 9 must be bent when the sensor 8 is inserted into the magnet circuit member 7. Thus, the automatic assembly of the device A can not be made at this portion.
Moreover, in the device A, the frame 4 is divided along the center of the axle 2, so that the small holes d1, d2 can not sufficiently hold the axle 2 and requires washers 3a, 3b to hold the axle 2. Also, when the coils are wound in the grooves e, the coils may slip inside the grooves to thereby cut the coil at an edge of the groove.
Thus, the Japanese Utility Model Publication (KOKAI) No. 64-55931 is not fully satisfactory.
Japanese Patent Publication (KOKAI) No. 54-49512 and No. 1-267622, also, disclose actuators for diaphragms of cameras, wherein a frame for a permanent magnet is divided horizontally into two parts, and terminals for receiving ends of coils are attached at a periphery of the frame. Japanese Utility Model Publication 62-197133 also shows the Similar device.
In the conventional devices, the terminals are all located at a periphery of the frame. Therefore, the arrangements of the coils, the pins and the conducting members on the printed board are inevitably limited. Also, assembly of the device is not easily or automatically made.
The present invention has been made in view of the drawbacks of the conventional actuation devices for the diaphragms of the cameras.
Accordingly, one object of the invention is to provide an actuation device for blades of light path or diaphragm of a camera, wherein pins for receiving ends of coils are arranged in a middle portion on a frame so that the ends of the coils can be attached to the desired pins.
Another object of the invention is to provide an actuation device as stated above, wherein a printed board with a magnet sensor can be easily assembled with the actuation device.
A further object of the invention is to provide an actuation device as stated above, wherein coils can be stably wound in required grooves without slipping and cutting of the coils.
A still further object of the invention is to provide an actuation device as stated above, wherein the arrangement of conducting members on a printed board attached to the actuation device can be made easily.
A still further object of the invention is to provide an actuation device as stated above, wherein the assembled device can be easily inspected without impairing a part of a printed board.
A still further object of the invention is to provide an actuation device as stated above, which can be easily and automatically assembled.
Further objects and advantages of the invention will be apparent from the following description of the invention.